AWIPS images of the MODIS fog/stratus product (above) and the corresponding GOES-12 fog/stratus product (below) revealed areas of fog that were forming in the valleys of Pennsylvania and New York around 08 UTC (4am local time) on 17 September 2007. The 1-km resolution MODIS imagery offered a more detailed view of the fog structure compared to the 4-km resolution GOES-12 product. Also note the “false signal” of fog that appeared on the GOES-12 image along certain land/water boundaries (the Finger Lakes region of New York, portions of Lakes Erie and Ontario, and the New Jersey coast of the Delaware Bay). With clear skies and light wind conditions associated with high pressure in place across much of the northeastern US, fog formation (due to strong radiational cooling during the night-time hours) was prevalent over a large area.